The Streptococci make up a medically important genera of microbes known to cause several types of disease in humans, including, for example, otitis media, conjunctivitis, pneumonia, bacteremia, meningitis, sinusitis, pleural empyema and endocarditis, and most particularly meningitis, such as for example infection of cerebrospinal fluid. Since its isolation more than 100 years ago, Streptococcus pneumoniae has been one of the more intensively studied microbes. For example, much of our early understanding that DNA is, in fact, the genetic material was predicated on the work of Griffith and of Avery, Macleod and McCarty using this microbe. Despite the vast amount of research with S. pneumoniae, many questions concerning the virulence of this microbe remain. It is particularly preferred to employ Streptococcal genes and gene products as targets for the development of antibiotics.
Infections caused by or related to Streptococcus pneumoniae are a major cause of human illness worldwide, and the frequency of resistance to standard antibiotics has risen dramatically over the last decade. Hence, there exists an unmet medical need for diagnostic tests and reagents for this organism.
Clearly, there exists a need for polynucleotides and polypeptides, such as the FabK embodiments of the invention that have a present benefit of, among other things, being useful to as diagnostic reagents. Such reagents are also useful to determine the frequency and geographical range of microbial strains.
A FabK enzyme, involved in fatty acid biosynthesis, has been recently reported from a strain of Streptococcus pneumoniae (Heath, et al. Nature 406: 145 (2000)). The present invention provides a variant form of FabK, differing at Thr 318.
The specific activity of the known enzyme under the published conditions was 64+/−4 nmol min−1, too low to efficiently perform certain biological analyses of the enzyme, such as detailed enzymological analyses (Heath, et al. Nature 406: 145 (2000)). The present invention solves this problem by providing a variant of the known FabK described, as well as method useful to perform detailed enzymological studies of FabK, wherein FabK activity is sufficient to perform such studies.
Moreover, the present invention provides a method of a diagnosing bacterial infection and bacterial genotyping using FabK polynucleotides and polypeptides.